Background Technical Information for
Carcinogenic Volatile Organic Compounds (cVOCs) Background Volatile organic compounds (VOCs) are a large group of carbon‐based chemical compounds that evaporate or sublimate easily at room temperature. The carcinogenic volatile organic compounds (cVOCs) are a subset of VOCs that that can cause cancer. Certain cVOCs) are federally regulated drinking water contaminants. Although there is no specific definition of a VOC, typical features are: 1) high vapor pressure and low water solubility, 2) boiling point greater than 200 °C, and 3) Henry’s Law constant greater than 0.01.
Key Issues In March 2010, the United States Environmental Protection Agency (EPA) announced a new approach to protecting drinking water and public health. The EPA’s new Drinking Water Strategy (DWS) is aimed at finding ways to strengthen public health protection from contaminants in drinking water by streamlining decision‐making, expanding protection under existing laws, and promoting cost‐effective new technologies to meet the needs of rural, urban, and other water‐stressed communities. One of the goals of the DWS is to address contaminants as groups rather than individually to enhance drinking water protection in a cost‐effective manner. In February 2011, the EPA identified carcinogenic volatile organic compounds (cVOCs) as the first set of contaminants to be addressed as a group (EPA 2012a). The EPA announced that it plans to develop one national primary drinking water regulation (NPDWR) covering up to 16 cVOCs (Table 1), including tetrachloroethylene (PCE) and trichloroethylene (TCE). PCE and TCE were previously identified in March 2010 as candidates for regulatory revision under a periodic review of existing NPDWRs. The cVOCs were chosen for the following reasons (EPA 2011): After carefully considering input from stakeholders, EPA decided to address as a group up to 16 volatile organic compounds (VOCs) that may cause cancer. The Agency determined that they represent a near term opportunity and also meet the factors listed in question 1: a) the public health goal for all is currently or would likely be set at zero because they may cause cancer, (b) most of this group of VOCs can be measured by the same analytical method (i.e., EPA 524.2), (c) many can be treated by the same treatment (i.e., aeration and/or granular activated carbon), and (d) a preliminary evaluation of occurrence indicates that some of these VOCs may co‐occur… Addressing these VOCs as a group will help reduce exposure to these contaminants.
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The primary health concern associated with the cVOCs as a group is their carcinogencity, or ability to cause cancer.
Table 1: List of 16 volatile organic compounds for potential grouping by EPA
Compound name
CASRN
Molecular Formula
Regulatory Status
1.
Benzene
71‐43‐2
C6H6
Currently regulated
2.
Carbon tetrachloride
56‐23‐5
CCl4
Currently regulated
3.
1,2‐Dichloroethane
107‐06‐2
C2H4Cl2 (Cl‐CH2‐CH2‐Cl)
Currently regulated
4.
1,2‐Dichloropropane
78‐87‐5
C3H6Cl2 [Cl‐CH(CH3)‐CH2‐Cl]
Currently regulated
5.
Dichloromethane
75‐09‐2
CH2Cl2 (Cl‐CH2‐Cl)
Currently regulated
6.
Tetrachloroethylene (PCE)
127‐18‐4
C2Cl4 (Cl2‐CH=CH‐Cl2)
Currently regulated
7.
Trichloroethylene (TCE)
79‐01‐6
C2HCl3 (Cl2CH=CH2Cl)
Currently regulated
8.
Vinyl chloride
75‐01‐4
C2H3Cl (CH2=CHCl)
Currently regulated
9.
Aniline
62‐53‐3
C6H7N (C6H5‐NH2)
Unregulated
10.
Benzyl chloride
100‐44‐7
C7H7Cl (C6H5‐CH2Cl)
Unregulated
11.
1,3‐Butadiene
106‐99‐0
C4H6(CH2=CH‐CH=CH2)
Unregulated
12.
1,1‐Dichloroethane
75‐34‐3
C2H4Cl2 (Cl2CH‐CH3)
Unregulated
13.
Nitrobenzene
98‐95‐3
C6H5NO2 (C6H5‐NO2)
Unregulated
14.
Propylene oxide
75‐56‐9
C3H6O[CH3‐CH(O)(CH2)]
Unregulated
15.
1,2,3‐Trichloropropane
96‐18‐4
C3H5Cl3 [Cl‐CH2‐CH(Cl)‐CH2‐Cl]
Unregulated
16.
Urethane
51‐79‐6
C3H7NO2 (H2N‐COO‐CH2‐CH3)
Unregulated
CASRN, Chemical Abstracts Service Registry Number
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Occurrence VOCs found in indoor air often originate from off‐gassing of coatings on consumer products such as carpeting and upholstery. According to the EPA (2012b), sources of VOCs found in indoor air include: “Household products including: paints, paint strippers, and other solvents; wood preservatives; aerosol sprays; cleansers and disinfectants; moth repellents and air fresheners; stored fuels and automotive products; hobby supplies; dry‐cleaned clothing.” VOCs can occur in drinking water sources as a result of contamination by spills or improper disposal of products containing VOCs. Leaking underground storage tanks (LUSTs) are a major source of VOCs to drinking water sources. The EPA has identified more than 514,000 releases from federally‐regulated LUSTs nationwide, and at least 78,000 have not yet been remediated (EPA 2013). The EPA estimates that VOCs are present in one‐fifth of the nation’s drinking water supplies (Zogorski et al. 2006). Analysis of VOCs in water can be accomplished using several techniques. Most commonly used is gas chromatography (GC) with a pre‐concentration step for sample enrichment (Golfinopoulos et al. 2001). Today, the most robust method for analyzing VOCs in water is through head‐space analysis using GC with mass spectrometric detection (HS GC‐MS). Most of the cVOCs can be analyzed using the same analytical method, EPA Method 524.2 (Eichelberger et al. 1992). Many of the cVOCs are likely to occur together, but occurrence data for the unregulated cVOCs are sparse. The United States Geological Survey (USGS) conducted a national survey of VOCs in US ground water and drinking water supply wells and found that about 1% or more of the aquifer samples contained VOCs (with a detection limit of 0.2 µg/L), and the concentrations were generally very low (USGS 2006). Four of the 16 cVOCs were among the 15 most frequently detected VOCs in the USGS survey (USGS 2006).
Health Effects The primary adverse health effect of interest for the cVOCs is carcinogenity, or ability to cause cancer. However, it is important to note that drinking water is only one of many sources of potential exposure to cVOCs, and the contribution of drinking water to a person’s total exposure may be trivial.
Guidelines Several cVOCs are currently federally regulated with maximum contaminant levels (MCLs) set at 0.002 mg/L to 0.005 mg/L (Table 2) (EPA 2012c). The EPA has also established one‐day and ten‐day health advisories for most of these compounds. 3
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Table 2: List of cVOCs currently regulated by EPA
Compound name
MCL (*)
Health Advisory (†) (10‐kg child)
1.
Benzene
0.005 mg/L
0.2 mg/L (One‐day) 0.2 mg/L (Ten‐day)
2.
Carbon tetrachloride
0.005 mg/L
4 mg/L (One‐day) 0.2 mg/L (Ten‐day
3.
1,2‐Dichloroethane
0.005 mg/L
0.7 mg/L (One‐day) 0.7 mg/L (Ten‐day)
4.
1,2‐Dichloropropane
0.005 mg/L
‐ 0.09 mg/L (Ten‐day)
5.
Dichloromethane
0.005 mg/L
10 mg/L (One‐day) 2 mg/L (Ten‐day)
6.
Tetrachloroethylene (PCE)
0.005 mg/L
2 mg/L (One‐day) 2 mg/L (Ten‐day)
7.
Trichloroethylene (TCE)
0.005 mg/L
‐ ‐
8.
Vinyl chloride
0.002 mg/L
3 mg/L (One‐day) 3 mg/L (Ten‐day)
Source: EPA 2012b Notes: * MCL (maximum contaminant level), the maximum allowable concentration of contaminant in drinking water supplied by public water systems. MCLs are set by the EPA under Federal regulations.
† Health Advisory (HA): an estimate of acceptable drinking water levels for a chemical substance based on health effects information; it is not a legally enforceable Federal standard, but serves as technical guidance to assist Federal, State, and local officials. One‐day HA: The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to one day of exposure. The One‐Day HA is intended to protect a 10‐kg child consuming 1 liter of water per day. Ten‐day HA: The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to ten days of exposure. The Ten‐day HA is also intended to protect a 10‐kg child consuming 1 liter of water per day.
Removal via Water Treatment Many of the cVOCs can be largely removed from water using the same treatment technologies: aeration or air stripping, adsorption to granular activated carbon (GAC), or advanced oxidation processes (AOPs) (Kommineni et al. 1999, EPA 2011). 4
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Action Items The EPA’s ongoing review of the cVOCs will provide an updated evaluation of the potential health effects of exposure to cVOCs and the likelihood of significant exposure through drinking water, as well as a determination about whether changes to regulations of these contaminants is likely to be effective.
References Eichelberger, J.W., J.W. Munch, and T.A.Bellar. 1992. “Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry.” EPA Method 542.2, Revision 4.0. August 1992. EPA Office of Research and Development, Environmental Monitoring Systems Laboratory. http://water.epa.gov/scitech/methods/cwa/bioindicators/upload/2007_11_27_methods_meth od_524_2.pdf Golfinopoulos, S.K., T.D. Lekkas, and A.D. Nikolaou. 2001. “Comparison of methods for determination of volatile organic compounds in drinking water.” Chemosphere 45(3): 275‐284. Kommineni, S., J. Zoekler, A. Stocking, S. Liang, A. Flores, and M. Kavanaugh. 1999. “Advanced oxidation processes.” In Treatment Technologies for the Removal of Methyl Tertiary Butyl Ether (MTBE) from Drinking Water: Air Stripping, Advanced Oxidation Processes, Granular Activated Carbon, Synthetic Resin Sorbents, Second Edition. NWRI‐99‐06. Fountain Valley, California: National Water Research Institute. http://www.nwri‐usa.org/pdfs/TTChapter3AOPs.pdf EPA (U.S. Environmental Protection Agency). 2011. Basic Questions and Answers for the Drinking Water Strategy Contaminant Groups Effort. EPA 815‐F‐11‐002. January 2011. http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/upload/FactSheet_DrinkingWaterStr ategy_VOCs.pdf EPA (U.S. Environmental Protection Agency).2012a. “Drinking Water Strategy.” Washington DC: EPA Office of Water. http://water.epa.gov/lawsregs/rulesregs/sdwa/dwstrategy/ EPA (U.S. Environmental Protection Agency). 2012b. “An Introduction to Indoor Air Quality (IAQ): Volatile Organic Compounds (VOCs).” Washington, DC: EPA Office of Radiation and Indoor Air, Indoor Environments Division. http://www.epa.gov/iaq/voc.html EPA (U.S. Environmental Protection Agency). 2012c. U.S. EPA‐OW. 2012 Edition of the Drinking Water Standards and Health Advisories. EPA 822‐S‐12‐001. Washington, DC: EPA Office of Water. http://water.epa.gov/action/advisories/drinking/upload/dwstandards2012.pdf EPA (U.S. Environmental Protection Agency). 2013. “The National LUST Cleanup Backlog: A Study of Opportunities.” Washington DC: EPA. http://www.epa.gov/oust/cat/backlog.html USGS (U.S. Geological Service). 2006. “The Quality of Our Nation’s Waters – Volatile Organic Compounds in the Nation’s Ground Water and Drinking‐Water Supply Wells.” Circular 1292. April 2006. http://pubs.usgs.gov/circ/circ1292/
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Zogorski, J.S., J.M. Carter, T. Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, and P.L. Toccalino. 2006. “Volatile organic compounds in the nation’s ground water and drinking‐water supply wells.” U.S. Geological Survey Circular, 1292, 101.
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